broken feathers, scaly balding patch and poop around vent

We have 6 Dominiques just over a year old-- 5 hens and one rooster. Over the last couple of weeks we've noticed a patch on the back of one of the hens that looked like she might have become a target for feather-picking, though frequent observation of the chickens showed none of this behavior (so at least they aren't doing it when we're watching?). Today, we noticed that this same hen now has a lot of poop around her vent. It isn't dried, so it's likely a recent thing, I guess, and it looks the usual color/consistency (of the runnier, brownish cecal variety of droppings), but there is a lot of it there. We took a closer look at the bald patch on her back (~4"x4") and while most of the spot has broken-off-looking feather shafts so that the contours of the feathers there lay flat, we see that on both sides of that spot she has a completely bald, scaly red patch. We aren't sure whether the bald spots are outside of the feather tract or not. Other than those symptoms, her behavior & appearance seem normal & healthy, and none of the other chickens are showing any signs of the same.

Other information that may or may not be helpful, just to make sure I've covered as much as I can:
-We are in south Louisiana
-They are in a ~10'x4' coop, with a ~20'x8' run.
-They get Purina Layena layer rations and occasional treats (fruits & veggies mostly) and water, of course!
-There hasn't been a drop or change in egg production (still averaging 4 per day from the 5 hens).
-Recent changes-- we usually feed the pellet food, but at the last trip to the feed store, there was only the granule food available (so same product, but different texture). We also recently changed the orientation of the run (dimensions pretty much the same), but we're pretty sure the feather issue started before that.

I hope that covers it. Any ideas about what might be going on and ways to handle it would be most appreciated!

First of all let me Since you have a roo, do you think he could be doing this to the hen, when breeding they grab hold of the feathers and eventually can break them off causing red skin and even wounds. as vfar as the messy poo, give her a good wash they really don't mind the after you have dried her clip the feathers from around her vent, that will keep the poo from sticking to all the fluff. also have you checked her for mites or lice, they can also make the chickens itchy and possibly cause this kind of problem. But I am leaning towards rooster, or feather picker. If it's rooster then you may want to get your hen a hen saddle. and also you can put blue- kote on the area to help heal the red skin and will also disguise the area in case of feather picker. your lay out sounds really nice and doesn't sound crowded at all for the # of birds you have. since none of the other chickens are showing this could also mean that she is the roos favorite too and he is just mating her to much.

One thing I learned when I discovered mites - gaaaccckkkk - was the way you can see them is to go into the coop at night with a flashlight and take a look at your hens' legs, etc. That was the only way - and it was by accident - that I discovered our mite infestation. Even the next morning, when I let them out of the coop, I could not see any signs of the mites from the night before. Sneaky things.

And I'm not sure, but I think I heard that messy butts are one sign of worms, so you might want to think about that. I'm trying Eprinex this week, it's a mite killer and a dewormer in one. If you think those could be possibilities.

I also think I remember reading on this forum that broken feathers are usually signs of mites, but I'm not going to swear by my memory on that.

We'll take a look in the coop with a flashlight to check for mites, but as we haven't noticed any drop in egg production or appetite, and none of the other hens have any feather problems two or three weeks after this first showed up with her, I'm inclined to go with the "popular with the rooster" theory. Also, we're pretty good about dusting the coop & run now & then with DE, so I'd hope that would have done its job in preventing mites.

A follow-up question-- a saddle seems like the way to go, but do we need to be concerned about the heat if she's wearing one of those? I'm not fully up to speed on how chickens regulate body temperature, but does it not cover enough of her to cause a problem with overheating? We're already getting pretty warm down here, and it's quickly getting hotter.

It could be a problem with heat chickens have a harder time with heat than cold, that being said. if you decide to go with the saddle talk to the person you order from there are several on BYC that make them and they might have mesh material so air can circulate through it but still provide protection. I know they make dogs halters out of it. hope this helps and all the best raising your flock.